Although prior techniques exist in the art for producing thin lines and features suitable for forming printed circuit boards (PCBs) or structures in PCMI, many of these techniques suffer from a number of significant disadvantages. For example, many previous techniques suffer from poor resolution. Moreover, techniques which do provide high resolution usually require complex apparatus such as sophisticated laser equipment. A further problem is that previous techniques have required the use of partially cured dry films of photopolymer. The thickness of these dry films has a detrimental effect on the resolution and/or definition of photoimaged surfaces. There are also problems in adhering partially cured dry films to substrates and contamination problems which once again causes problems in the photoimaging process.
It is believed that no 100% solids energy curable coating heretofore available is able to cure with UV energy levels below 20 mJ for use with the photoimaging process herein described to producing images for use within the PCB or the PCMI.
Consequently, it is believed that a PCB prepared using a 100% solids resist over copper imaged using a photo mask with the photoimaging process herein described is a new article of manufacture. Previously, all Liquid Photo Imageable (LPI) materials have contained solvent and required pre drying prior to curing. Therefore the successful use of a 100% solids coating is a novel approach.
The present application is an extension of previous applications by the present applicant such as WO 2010/007405 and WO 2012/069807, which are incorporated herein by reference. The techniques described therein are known as the ‘Rainbow Coating Process’ which can be used in photoimaging processes.
It is an object of at least one aspect of the present invention to obviate or mitigate at least one or more of the aforementioned problems.
It is a further object of at least one aspect of the present invention to provide a 100% or substantially 100% solids energy curable coating material for use in a photoimaging process.